How to Mix Neem Oil for Plants: DIY Natural Insecticide Spray

Neem oil derives from the neem tree (Azadirachta indica), a plant native to India. Growers harvest azadirachtin, an active ingredient, from neem seed kernels through a cold-press extraction process to make organic neem oil. Cold-pressed neem oil is a common insecticide in organic gardening pest control.

When you spray neem oil on leaves, it gives the foliage a sheen, creating a protective coating for the leaves that will only affect insects who feed on the outer layer of the plant. Since neem oil is oil-based, you should use it in moderation for any produce crops that humans or animals will ultimately consume. The oil can affect the taste of your veggies but can also be harmful to children or small animals if they consume higher concentrations. Neem oil works to deter the spread of plant diseases or predatory insects, like caterpillars, but does not harm beneficial insects or pollinators that promote healthy plant growth and reproduction.

You can find various neem oil products available for purchase at your local gardening or home improvement store, but you should research the ingredients thoroughly. Some store-bought neem oil products contain synthetic compounds that, in high doses, can harm plants or people. Alternatively, you can make your own neem oil spray at home. Follow these steps to produce a gallon of neem oil spray:

1. 1. Prepare the emulsifier agent. Since oil and water will separate, you must add an emulsifier agent before mixing the two. You can add liquid dish detergent or silica to roughly eight ounces of water to act as your mixing agent.
2. 2. Fill a bucket with warm water. If you wish to mix a gallon of neem oil spray mixture, fill the bucket or pump sprayer with enough water to almost reach the gallon mark. If you wish to add aloe vera powder to promote plant immunity and growth, feel free to mix in a quarter teaspoon at this time.
3. 3. Emulsify the pure neem oil. Mix the emulsifier agent with the pure neem oil in a separate container. Use one tablespoon of neem oil and one teaspoon of liquid soap or silica. Mix thoroughly before you add into the bucket or pump sprayer. If you have sufficiently emulsified the oil, there should be no bubbles of oil forming at the surface.
4. 4. Add the emulsified neem oil to the bucket or pump sprayer. You will now have a gallon of neem oil spray ready to apply to your plants. If you wish to use smaller spray bottles to easily transport the mixture, you can begin to transfer the neem oil spray from the bucket. Just ensure you clean all of your mixing equipment and utensils so they’re ready for future use.

You can use neem oil spray to deter a number of pests and diseases that can spread into a full-blown infestation of your vegetable garden or flower bed. You can treat the following with a DIY neem oil mixture or store-bought neem oil product:

1. 1. Aphids: Larvae will hatch from winter eggs attached to the undersides of plant leaves. As aphids grow they will feed on the leaves similar to other predatory bugs like thrips. Once the first signs of browning or wilting leaves appear, you can apply neem oil to your plant. Additionally, you can introduce ladybugs, which are natural predators of aphids.
2. 2. Black spot: Although neem oil works as an insecticidal soap to clean and protect your plant’s surface, it can also be a fungicide for treating black spot and anthracnose. These fungi will appear as dark circular spots or holes on the leaves of plants that do not receive the direct sunlight they require.
3. 3. Nematodes: These microscopic organisms can feed on every part of a plant. Unlike easier-to-spot surface pests, like Japanese beetles or mealybugs, nematodes can attack a plant’s root system at a cellular level. To effectively treat the spread of nematodes, you can use the “soil drench” technique by diluting concentrations of pure neem oil with warm water and then lightly pouring the mixture around the root base.
4. 4. Powdery mildew: Plants with limited spacing are prone to the spread of this white, fuzzy fungus, especially in humid conditions. Other than neem oil insecticide, you can use natural soap containing potassium bicarbonate as a foliar spray. Simply mix half a teaspoon of liquid soap or dish soap to a gallon of water and then apply the mixture with a spray bottle to the affected leaves.
5. 5. Spider mites: You need to first identify spider mites before you can begin treatment. Simply take a small sheet of paper and hold it beneath an infected leaf. Lightly tap or shake the leaf. If spider mites are present, you should see them land onto the paper’s surface. Neem oil kills spider mite reproduction by coating the membrane of the eggs and preventing the larvae from hatching.
6. 6. White flies: The grubs or larvae of white flies are hard to spot, but they will feed on leaves and produce a substance called “honeydew” that can subdue photosynthesis. Similar to fungus gnats, these winged pests can fly from plant to plant and reproduce quickly. Therefore, the most effective strategy in dealing with white flies is consistent plant inspection and prevention with an insect repellent.

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